code: def _get_key(self):
      if self.source is None:
          return []
      elif isinstance(self.source, hl.Table):
          if self == self.source._row_indices:
              return list(self.source.key)
          else:
              return []
      else:
          assert isinstance(self.source, hl.MatrixTable)
          if self == self.source._row_indices:
              return list(self.source.row_key)
          elif self == self.source._col_indices:
              return list(self.source.col_key)
          else:
              return []
  
file_path: hail/hail/python/hail/expr/expressions/indices.py
imports: from hail.typecheck import typecheck_method, anytype, setof
  import hail
  from typing import List
label_desc: Use image node_id 7 for calling the Indices obj's underlying member method code with example usage: obj._get_key() and returns: list, list, list, list, list, list